This invention relates to an inkjet printhead chip. In particular, this invention relates to a configuration of an ink jet nozzle arrangement for an ink jet printhead chip.
Many different types of printing have been invented, a large number of which are presently in use. The known forms of printers have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.
In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.
Many different techniques of ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, xe2x80x9cNon-Impact Printing: Introduction and Historical Perspectivexe2x80x9d, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).
Ink Jet printers themselves come in many different types. The utilization of a continuous stream of ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.
U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein a high frequency electrostatic field modulates the ink jet stream to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al).
Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.
Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques which rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Manufacturers such as Canon and Hewlett Packard manufacture printing devices utilizing the electro-thermal actuator.
As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high-speed operation, safe and continuous long-term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction, operation, durability and consumables.
In Application number U.S. Ser. No. 09/112,767 there is disclosed a printhead chip and a method of fabricating the printhead chip. The nozzle arrangements of the printhead chip each include a micro-electromechanical actuator that displaces a movable member that acts on ink within a nozzle chamber to eject ink from an ink ejection port in fluid communication with the nozzle chamber.
In the following patents and patent applications, the Applicant has developed a large number of differently configured nozzle arrangements:
The above patents/patent applications are incorporated by reference.
The nozzle arrangements of the above patents/patent applications are manufactured using integrated circuit fabrication techniques. Those skilled in the art will appreciate that such techniques require the setting up of a fabrication plant. This includes the step of developing wafer sets. It is extremely costly to do this. It follows that the Applicant has spend many thousands of man-hours developing simulations for each of the configurations in the above patents and patent applications.
The simulations are also necessary since each nozzle arrangement is microscopic in size. Physical testing for millions of cycles of operation is thus generally not feasible for such a wide variety of configurations.
As a result of these simulations, the Applicant has established that a number of common features to most of the configurations provide the best performance of the nozzle arrangements. Thus, the Applicant has conceived this invention to identify those common features.
According to the invention there is provided an ink jet printhead chip that comprises
a wafer substrate,
drive circuitry positioned on the wafer substrate, and
a plurality of nozzle arrangements positioned on the wafer substrate, each nozzle arrangement comprising
nozzle chamber walls and a roof wall positioned on the wafer substrate to define a nozzle chamber and an ink ejection part in the roof wall,
a micro-electromechanical actuator that is connected to the drive circuitry, the actuator including a movable member that is displaceable on receipt of a signal from the drive circuitry, the movable member defining a displacement surface that acts on ink in the nozzle chamber to eject the ink from the ink ejection port, wherein
the area of the displacement surface is between two and ten times the area of the ink ejection port.
The movable member of each actuator may define at least part of the nozzle chamber walls and roof wall so that movement of the movable member serves to reduce a volume of the nozzle chamber to eject the ink from the ink ejection port. In particular, the movable member of each actuator may define the roof wall.
Each actuator may be thermal in the sense that it may include a heating circuit that is connected to the drive circuitry. The actuator may be configured so that, upon heating, the actuator deflects with respect to the wafer substrate as a result of differential expansion, the deflection causing the necessary movement of the movable member to eject ink from the ink ejection port.
The invention extends to an ink jet printhead that includes a plurality of inkjet printhead chips as described above.